1. Field of the Invention
This invention relates to stereoscopic three-dimensional displays. Particularly, this invention relates to systems and methods for the alignment of stereoscopic three-dimensional displays such as may be employed in aerospace applications.
2. Description of the Related Art
Stereoscopic three-dimensional displays function through the synchronized presentation of different images to the left and right eyes of a user. In principle, the images are differentiated to simulate the parallax that would naturally occur between two eyes of a viewer if actually present at the camera location. Thus, the brain can process the differentiated images normally to provide depth perception to the user. Alignment of the separate images at the point where they are received by the separate eyes is an important factor in the development of any stereoscopic three-dimensional display system.
Mismatch between display geometry and camera geometry can cause operational inefficiency of the application employing the display, visual fatigue, and image distortion, among other negative effects. Such mismatch can result in errors and unsafe operation of remotely-controlled equipment employing the display system. Operators will suffer visual fatigue, discomfort, and/or headaches, limiting the allowable operational period. Such displays present distorted and/or mis-aligned images. Such systems can suffer from operator complaints which may ultimately lead to abandonment of the poorly performing stereoscopic three-dimensional display system.
However, correct binocular alignment of a dual-image stereoscopic three-dimensional display can be complicated and prone to error. In addition, proper alignment of such displays typically requires special expertise not always available. Because of these and other factors, it is usually not practical to employ a single dual-channel stereoscopic three-dimensional display applied to different imaging geometries (e.g. different input cameras), since this would require time-consuming and difficult re-alignment of the display to match inputs from a different imaging geometry.
Currently available stereoscopic three-dimensional displays are therefore limited, practically, to use with only one type of input geometry, since it is often too difficult to change back and forth between different input imaging configurations. For example, the correct alignment of display elements inside a dual-channel stereoscopic three-dimensional display depends on the convergence angle of the left and right cameras, and whether this convergence is accomplished by toe-in of the cameras or by lateral shifting of the lenses relative to the imaging chips.
If an operator could simply select the input imaging parameters on the display unit, such as camera field of view, convergence distance, and convergence toe-in angle, the stereoscopic three-dimensional display could be designed to provide assistance in correctly aligning the display geometry to match the imaging geometry, either by automatically moving the display components, or providing visual feedback to the operator with easy-to-use test patterns that allow for accurate manual alignment.
Current stereoscopic three-dimensional displays do not provide assistance in or accommodate the need for alignment of left and right display images to correctly match imaging system geometry (e.g., camera convergence and alignment). When imaging geometry is complex, due to camera convergence, and left and right display-channel components are viewed through refractive and reflective optical elements, the process of correct alignment is difficult and requires expertise not always available.
There are some existing auto-alignment techniques used for aligning multiple projectors in non-stereo simulator displays. Separately, Barco has mentioned an alignment system using lasers for their large-screen stereoscopic theater system. Some auto-convergence systems and test patterns have been previously developed for 3-tube CRT video projectors in the previous decades for matching up the red, green, and blue projected images, however, such techniques are not directly applicable to the alignment of stereoscopic three-dimensional displays. For example, they incorporate no concept of aligning two distinct images, one for each eye, to create a three-dimensional perception. Such systems are directed to the alignment of different components of the same image. In addition, current stereoscopic three-dimensional systems do not provide the means for an operator to check and/or adjust the display alignments required for different camera configurations.
U.S. Pat. No. 4,298,176 by Kendall, issued Nov. 3, 1981, describes a refueling system, for use in a tanker aircraft from a remote location without a direct out-the-window view of the refueling operation, having enhanced three-dimensional viewing of the refueling operation by use of multiple video cameras, polarized video monitors and cross-polarized eye glasses together with controls for movement of the boom tip in elevation and azimuth, as well as controls for extension of the boom tip.
U.S. Pat. No. 6,703,988 by Fergason, issued Mar. 9, 2004, describes a display system or monitor arrangement for stereoscopic three-dimensional displaying of images including a pair of displays for providing respective left eye and right eye images and arranged in perpendicular intersecting planes, a beam splitter for combining the images from the displays in a common light path, and a means to discriminate between respective images to present the respective left and right eye images to the eyes of a viewer for viewing. Image discriminating functions may be obtained using plane polarized light characteristics and/or circular polarized light characteristics. A package arrangement retains the display a system components for storage or use; and a cubical mount structure may provide alignment and positioning of respective parts of the display system. Display methods for displaying stereoscopic images in a common light path are included.
U.S. Pat. No. 6,593,957 by Christie, issued Jul. 15, 2003, describes autostereoscopic image displays providing realistic three-dimensional images to one or a plurality of viewers without the need for wearable appliances. In some embodiments, the images are viewed through a beamsplitter, while in other embodiments the viewer observes the images on a display screen. A viewer-tracking system monitors the viewer's movements and directs each image of a stereopair to the proper eye of the viewer. In some embodiments, the stereoimages are kept independent and separately directed through differential polarization. In other embodiments, this is accomplished through selective intensity modulation.
U.S. Pat. No. 5,976,017 by Omori et al., issued Nov. 2, 1999, describes a stereoscopic-image game playing apparatus displaying a screen image for right eye and a screen image for left eye on an LCD, outputs images of the player obtained by cameras to the receiving side, and displays images corresponding to the right half face and the left half face of the player based on the player's images on a second LCD. The images displayed on the second LCD are used as figures for selectively introducing lights from the screen images on the first LCD, by a lens, to the right and left eyes of the player. This enables stereoscopic vision without glasses for separating images respectively for the player's right and left eyes, and allows the player to move from the initial position.
U.S. Pat. No. 5,644,427 by Omori et al., issued Jul. 1, 1997, describes screen images for the right eye and for the left eye are displayed upside down on two image display devices, respectively, and images of right half and left half faces of the viewers picked-up by two image sensing devices are displayed on two spatial modulation elements. By seeing the screen images transmitted through the images of the right half and the left half faces, which are light transmission images, on the spatial modulation elements, and through lenses, having directivities, the right eyes and the left eyes of the viewers can respectively see the screen images for the right eyes and for the left eyes, which are combined by a half mirror.
U.S. Pat. No. 6,069,649 by Hattori, issued May 30, 2000, describes a stereoscopic three-dimensional display which enables plural persons to simultaneously observe stereoscopic images includes a color liquid crystal plate for displaying stereo-pairs composed of left and right eye perspectives in time-interlaced manner, a monochrome TV display disposed behind the color liquid crystal plate for displaying binary and inverted binary images of half face of each observer so as to be synchronized with the time-interlaced display of the color liquid crystal plate, and a large convex lens disposed between the color liquid crystal plate and the monochrome TV display so as to focus the observers' optical images on the screen of the monochrome TV display in geometrical agreement with the observers' face images displayed thereby. And an infrared TV camera is disposed so as to take observers' images by way of the large convex lens and input observers' face images to the monochrome TV display.
U.S. Pat. No. 5,774,175 by Hattori, issued Jun. 30, 1998, describes a stereoscopic television which enables plural observers to simultaneously observe a stereoscopic images includes a color liquid-crystal plate, a monochrome TV display disposed behind the liquid-crystal plate, and a large format lens disposed between the color liquid-crystal plate and the monochrome TV display so as to focuss the observer's image on the screen of the TV display. The color liquid-crystal plate alternately displays stereo-pairs composed of left and right eye perspectives, and the monochrome TV display alternately displays inverted binary images of half face of each oberver. The large format lens distrubutes light emitted from the inverted binary images of half face of each observer to the left and right eyes of each observer through the color liquid-crystal plate, whereby the left and right eye perspectives of the stereo-pairs displayed by the liquid-crystal plate respectively reach the left and right eyes of each observer.
In view of the foregoing, there is a need in the art for apparatuses and methods for efficiently and accurately aligning stereoscopic three-dimensional displays. There is also a need for the applicable alignment hardware to be integrated into a stereoscopic three-dimensional adding minimal additional weight or complexity. There is further a need for a sterepscopic display to be adaptable and readily adjustable to be aligned to different camera geometries. There is further a need for such systems and apparatuses in aerospace applications. As detailed hereafter, these and other needs are met by embodiments of the present invention.